perf: use fma for m3_update

Author: Alvaro-Kothe

pandas/_libs/window/aggregations.pyx

@@ -2,6 +2,7 @@
 
 from libc.math cimport (
     fabs,
+    fma,
     round,
     signbit,
     sqrt,
@@ -532,7 +533,7 @@ cdef void add_skew(float64_t val, int64_t *nobs,
         delta_n = delta / n
         term1 = delta * delta_n * (n - 1.0)
 
-        m3_update = delta_n * (term1 * (n - 2.0) - 3.0 * m2[0])
+        m3_update = delta_n * fma(term1, n - 2.0, -3.0 * m2[0])
         new_m3 = m3[0] + m3_update
         if fabs(m3_update) + fabs(m3[0]) > 1e10 * fabs(new_m3):
             # possible catastrophic cancellation
@@ -559,7 +560,7 @@ cdef void remove_skew(float64_t val, int64_t *nobs,
         delta_n = delta / n
         term1 = delta_n * delta * (n + 1.0)
 
-        m3_update = delta_n * (term1 * (n + 2.0) - 3.0 * m2[0])
+        m3_update = delta_n * fma(term1, n + 2.0, -3.0 * m2[0])
         new_m3 = m3[0] - m3_update
 
         if fabs(m3_update) + fabs(m3[0]) > 1e10 * fabs(new_m3):